The present invention relates generally to photovoltaic systems for converting sunlight to electrical power, and more particularly to a novel system for directing light onto enclosed photovoltaic arrays for electrical power generation in remote applications.
Existing solar photovoltaic array structures are substantially limited to planar (flat) arrays of large size to provide sufficiently high power for remote power applications such as aboard orbiting spacecraft. Since storage capacities of launch vehicles for space applications are severely limited, flexible planar arrays were developed consisting of photocells on flexible substrates which may be stored in rolled or folded condition and selectively deployed after orbit insertion. The flexible arrays suffer from distinct shortcomings in that large structures are required for high power systems, and inherent dynamic instability exists in the deployed array because of the light weight of materials used as substrates combined with substantial extension of the array for operation. Deployment mechanisms for flexible arrays can be complicated, expensive, and heavy. The large area subtended by the deployed flexible array subjects the constituent solar cells to substantial meteoroid and particulate radiation impingement hazard which necessitates use of protective coverglasses for the cells. The exposed surfaces also limit operating voltages due to space plasma interactions. Photovoltaic arrays having optics which concentrate sunlight onto individual cells provide some protection from impact, but present a weight penalty and require multiple complex and expensive optical collectors.
The present invention solves or substantially reduces in critical importance the aforementioned shortcomings in existing photovoltaic systems by providing a photovoltaic power system particularly applicable for use in providing electrical power to systems of orbiting spacecraft or other remote environments. A conventional hollow prismatic light tube of square cross section, smooth inner surfaces, and grooved outer surface is provided with a plurality of photovoltaic cells mounted in four rectangular arrays on thin substrates attached to the grooved surfaces with the cells inwardly facing of the light tube. Light concentrating optics are disposed at the light receiving end of the light tube to illuminate the tube and cells with maximum intensity, and may be configured to concentrate into the light tube sufficient light for each cell in the arrays equivalent in intensity to that of the surrounding environment.
The invention has substantial utility for powering spacecraft systems requiring high power in remote locations. The system of the invention may be configured in modular form, is lightweight, and is minimally vulnerable to damage by particulate impact, and consequently has maximum mission lifetime.
It is, therefore, a principal object of the invention to provide an improved photovoltaic system for conversion of sunlight to electrical power.
It is a further object of the invention to provide a modular photovoltaic system for remote mission applications.
It is a further object of the invention to provide a compact photovoltaic system for applications aboard orbiting spacecraft.
It is yet another object of the invention to provide a photovoltaic system which is protected against radiation damage and particle impact.
These and other objects of the invention will become apparent as the detailed description of representative embodiments proceeds.